Study on the Electromagnetic Coupling Characteristics of the Initiating Explosives Based on the Dielectric Polarization Theory

In this article, the coupling mechanism of microwave to initiating explosives (IEs) is proposed based on the dielectric polarization theory. An open-ended coaxial probe (OECP) with short-circuited terminal and single-layer samples is developed to measure the reflection coefficient of the IEs, which are powder materials with extremely limited samples (milligrams). Then, the complex permittivity (CP) (
$\varepsilon ^{\prime }-{j}\varepsilon ^{\prime \prime }$
) of IEs can be inversed based on the spectral-domain model and the main-mode reflection coefficient. The proposed method can be applied to measure the CP of IEs within 1–18 GHz, and its accuracy is verified by alumina powders whose permittivity is known, which proves that the error is within 10%. The measured CP can be applied to establish the electromagnetic coupling model of IEs. Two kinds of IEs, i.e., HY-5 and HY-6, were taken as examples, and the dependence of their CP on the frequency was figured out. Thus, their microwave absorption factors (
$\varepsilon ^{\prime \prime }-{f}$
) could be obtained. The electromagnetic coupling effect of HY-6 was investigated with a multiphysical simulation method, and the temperature rise characteristics of HY-6 under microwave irradiation at different frequencies were compared. The results indicate that the maximum temperature rise happens at 17 GHz, where the microwave absorption factor is the largest. The research results can be applied to guide the electromagnetic protection and storage of IE devices (IEDs) and benefit the frequency selection for microwave ignition systems, as well as the development of microwave-sensitive IE devices.